Wellburn Interchange is junction 10 of the M74, and lies at the northern end of Lesmahagow. It was built in 1986 as part of the first southern extension of the original M74 (see M74 and A74(M) History), which extended to junction 12 at Happendon, and is now well known as the two lane section of the route. The junction is a dumbbell junction with the B7078 crossing over the top of the motorway. However, there is a slip road missing, with the M74 southbound off slip missing, this movement being served by the single slip Junction 9 a short distance to the north. The three sliproads are all single lane, and the two roundabouts relatively small. Each of them has a fourth arm, running at right angles to the M74 and parallel B7078. On the north eastern side this is only a farm access, but on the south western side Teiglum Road leads into an industrial estate, passing the towns relatively new supermarket and a busy truckstop.
To the north the B7078 is single carriageway, but to the south of the junction, the B7078 heads into Lesmahagow, quickly becoming dual carriageway as the route picks up the old A74. This was the start of the longest surviving section of dual carriageway from the old road, albeit hardly changed since the motorway opened, meaning that the surface is old and worn, but otherwise gives a good taste of what the old A74 was like. In recent years, however, the dualled section has become notably shorter, with the southern section reduced to a single carriageway with parallel cycle route. It is now only just over a mile long, approximately the same as the section between junctions 11 and 12.